JET PROPULSION

A jet engine produces thrust from a roaring jet of super-hot gas. Its construction looks complicated, but the way it works is very simple. A powerful jet of gas moving in one direction produces thrust in the other direction. Imagine you are standing on a skateboard and squirting a powerful hose forward. Jet propulsion will push you backward. This reaction has been known for nearly 2000 years, but it was not until the 1930s that it was applied to an engine.

In the first experiment, you can make a jet zoom along a string. The jet engine is like a balloon that produces thrust from escaping air. The second project demonstrates how a turbine works. Hot air produced by the gas jet turns the blades of the turbine. The turbine drives the fan at the front of the jet engine. These projects may seem simple, but they use the same scientific principles that propel all jet airplanes through the air.

BALLOON JET

Long, thin balloon, scissors, tape, drinking straw, string.

STEP 1
Blow up the balloon and, while a friend holds the neck, tape the straw to its top. Thread the string through the straw and, holding it level, tie it to something to keep it in place.

TURBINE LIGHTS

Aluminum pie tin, scissors, compass, protractor, ruler, pin, 3in length of 1/8in dowel, tape, bead, thread reel, nonhardening modeling material, plate, four night light candles, matches.

STEP 1
Using scissors cut out the bottom of a large aluminum pie tin as evenly as possible. Make a small hole in the center with the point of the compass.

STEP 2
Mark a smaller circle in the center. Use a protector to mark 16 equal sections of 22.5 degrees, and cut along each one to the inner circle. Use one scissor cut along each line, if possible.

STEP 3
Angle the blades by holding the inner tip and twisting the outer edges 20 to 30 degrees. The center of the inner tip should be flat, in line with the center of the disk.

STEP 4
Tape the blunt end of the pin to one end of the dowel. Finish it off neatly and trim if necessary. Place the bead on the pin. This will allow the finished turbine to spin freely.

STEP 5
Put the dowel in the reel into the modeling material in the center of the plate. Place the four candles on the plate around the reel.

Place the hole in the center of the turbine over the pin. Ask an adult to light the candles. Hot air will spin the blades.